How do I control the quality of JPEG images?

Question

I've written a program that scales a set of JPEG images down to various dimensions. I'm happy with the speed of execution, but quality of the images could be better. How do I specify the quality of the JPEG images I create? In graphics editors, I'm given the option of controlling the lossy-ness (?) of JPEGs when I save them, either reducing image qualify to shrink the file size or vice versa. How can I do this programmatically?
Thanks

Answer 1

Hi Jhm,
leaving aside the scaling algorithm, to save an arbitrary image with 100% quality you'd use
something like the following code snipet below
regards,
Owen
// Imports
import java.awt.image.*;
import com.sun.image.codec.jpeg.*;
public boolean saveJPEG ( Image yourImage, String filename )
    boolean saved = false;
    BufferedImage bi = new BufferedImage ( yourImage.getWidth(null),
                                           yourImage.getHeight(null),
                                           BufferedImage.TYPE_INT_RGB );
    Graphics2D g2 = bi.createGraphics();
    g2.drawImage ( yourImage, null, null );
    FileOutputStream out = null;
    try
        out = new FileOutputStream ( filename );
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder ( out );
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam ( bi );
        param.setQuality ( 1.0f, false );   // 100% high quality setting, no compression
        encoder.setJPEGEncodeParam ( param );
        encoder.encode ( bi );
        out.close();
        saved = true;
    catch ( Exception ex )
        System.out.println ("Error saving JPEG : " + ex.getMessage() );
    return ( saved );
}